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Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 191
Registered: 6-2003
| | Posted on Tuesday, June 08, 2004 - 11:58 am: | 
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I have my ideas about this one, but some of the guys around here have been debating over amp pull when a radio swings forward in modulation. To clarify, some say the swing does not pull anymore amps but others say the swing pulls as much amps as if the radio keyed up as many watts constant. Example: one radio keys 10 watts and swings up to 30 watts; another radio keys 30 watts but no swing. Do they draw the same amps from the power supply? |
Tech548
Moderator
Username: Tech548
Post Number: 101
Registered: 5-2004
| | Posted on Wednesday, June 09, 2004 - 1:19 am: |
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Mikefromms
Yes, they certainly do. One is a constant draw and the other one isn't.
If you have an Amp Meter on the power supply or somewhere in line, you would see that the amperage draw would be the same for both radios.
As an example, lets say that one 30 watt radio draws 10 amps constant because there is no upwards swing in power. In other words, it deadkeys with 30 watts of power.
And the other 30 watt radio will "swing" up to 30 watts when modulated. Both radios will require the same amount of amperage draw at 30 watts.
Another example... Lets say that you have two identical 250 watt linears and two identical radios with both of them capable of 20 watts. The radio that deadkeys 20 watts will instantly take the linear to its max 250 output power with a amperage draw of (lets say) 30 amps. And the radio that will swing to 20 watts will also take its linear to 250 watts with the same amount of amperage draw.
An amp meter will easily settle your argument.
Jeff. |
Tech8541
Moderator
Username: Tech8541
Post Number: 216
Registered: 12-2003
| | Posted on Wednesday, June 09, 2004 - 11:11 pm: |
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mike,
the amp meters in all power supplies are rms, and the 250w of swing will not show the same amp draw that a 250w carrier will. same for the 30w of swing and 30w of carrier. the amp draw -is- the same, but the rms meter will not show that.
take the 250w linear for example. if the linear was modulated so its output was at 100% modulation (250w) then this would equate to a 62.5w carrier. lets say this 62.5w carrier shows 14amps. when the amp is modulated to produce 100% modulation (250w) the needle will still show 14amps since the amp meter is a rms meter and not a peak meter. if you made the amp deadkey 250w you would see double this, about 28amps. with both the 250wpep and the 250w of carrier power, the amp is pulling 28amps, but the amp meter can only show this 28amps under a continuous output like a carrier.
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